Safety load limiting means for hoists and the like



June 20, 1950 R. R. DILLON 2,512,055 SAFETY LOAD LIMITING MEANS FORHoIsTs AND LIKE Filed .June 1947 @f 65W il Patented June 20, 1950 SAFETYLOAD LIM'ITING MEANS FOR HOISTS AND THE LIKE Ralph R. Dillon, Chicago,Ill., assigner to W. C.

Dillon & Company, Inc., Chicago, Ill., a corporation of IllinoisApplication June 4, 1947, Serial No. 752,326

6 Claims. 1

This invention relates to a means to make safe the operation of hoistsand the like by positively preventing any overloading of the hoist.

One object of the invention is to provide a load limiting means in theform of a device that weighs the load, and if the load exceeds apredetermined safe weight the means for operating the hoist is renderedinoperative thereby notifying the operator of the hoist of such fact andat the same time preventing any possibility of unsafe operation due toan overload on the hoist.

Another object is to provide means which is simple and inexpensive inconstruction and readily adaptable for connecting in the electriccircuit of the hoist operating motor for serving to limit the load, thuspreventing any possibility of either accidental or intentionaloverloading of the hoist.

Still another object is to provide an element interposed at any pointbetween a stationary support and the load being hoisted for the purposeof controlling an electric circuit that renders the hoist operatingmotor inoperative to further lift the load whenever the load causes thesafety load limiting means to assume its operative position.

A further object is to provide a special link interposed between asupport and the load, which link is extensible in proportion to load,which carries an electric switch and which so operates the switch as tomove it to hoist motor de-energizing position at a predetermined loadingof the hoist.

Still a further object is to provide the switch carried by the speciallink connected in the lifting circuit of the hoist motor but soconnected with anrelectric switch for the motor that the switch can beoperated to the reverse position for lowering the load independent ofthe load limiting switch, thereby making it possible to lower the loadsuiciently to release all or part of it upon the lifting circuit of thehoist motor being rendered inoperative by the load limiting switch.

With these and other objects in view, my invention consists in theconstruction, arrangement and combination of the various parts of mydevice whereby the objects contemplated are attained, as hereinaftermore fully set forth, pointed out in my claims and illustrated in theaccompanying drawings, wherein:

Figure 1 shows a motor driven chain hoist (Cl. S18-488) switch, theswitch being adjusted to lift a load,

Figure 5 is a similar .view showing the control switch adjusted forlowering the load, and

Figure 6 is a sectional view on the line 6-6 of i Figure 5 showing ythe-switch in neutral position.

On the accompanying drawing I have used the reference character LS toindicate a limit switch of a safety load limiting means indicated ingeneral at A. AThe switch LS comprises terminals Il and I2 and a switchblade 22 adapted tovnor= mally establish a circuit across the terminals.

The blade 22 is normally held in the downwardlyl bowed position ofFigures 2 and 4 by an actuating pin 24 against which an adjusting screw25 rests.

The screw 25 is carried by a U-shaped frame 23 having an arm 26 extendedfrom the upper leg toward the lower-,leg of the U. This frame ispreferably made of tool steel cut to the shape shown and then hardenedso that it will carry a substantial load without breaking when inter--posed in a hoist line. It may be connected in the line by means of studs21 .and 28 which by way of example are shown connected with a supportinghook 29 and a hoist H respectively in Figure 1. A support 30 is shownfor the hook 29 and the hoist H has extended therefrom a lifting chain32 terminating in a load engaging hook 30.

The safety load limiting means A may be placed instead just above thehook 3| and can be connected with the hoisting cable of a `crane orelevator as it is applicable to any type of hoisting mechanism. The typeof hoist shown in Figure 1 .is merely for the purpose of illustration.

'I'he limit switch LSk may be supported onthelowerleg of the U frame bymeans of a plate 39 riveted at 40 to the arm, screws 4| being providedto mount the switch housing on the plate. The

switch terminals Il and l2 are connected in a.

circuit with the motor M and a control switch therefor which is showndiagrammatically in.

Figures 4 and 5. The control switchr consists o f .a rotor 2| rotatableabout one-fourth turn be- 3 tween upper brushes I, 2, 3 and 4 and lowerbrushes 5, 5 and l.

The motor M has a starting coil SC connected with the brushes 2 and il,a centrifugal switch CS being in the circuit or any suitable switch maybe used for cutting out the starting coil after the motor gets up tospeed. The motor also includes a running coil RC connected to thebrushes 3 and 6. The brush I is connected with terminals 8 and I 2 withthe circuit branching at a terminal I0, and the brush 5 is connectedwith the terminal II ofthe limit switch. The terminal B is a currentsupply terminal and a second one is provided indicated at 9. Theterminal 9 is con.- nected with the brush 1.

The rotor 2l of the control switchhas thereincurrent conducting bars I3,I4, I5, I6, 11, I8, I9 and for connecting the various brushes I to lwith each other in a desired iriiit path,

Normally the conductors I3 to 2D are out of contact with all the brushesI to 'I and the rotor is in the position of Figure 6. The rotor has across bar 33 normally retained in the position shown in Figure 6 byopposing springs 34and 35. It can be rotated an eighth of a turn ineither direction however by pull wires 36 and 3g?, extend'- ing to acontrol bar 38, rI lhis bar maybe manipulatedlfer causing rotation ofthe motor `Min either i direction for either raising or lowering the:load

as desired, and when the control bar is released the rotor '2I returnsto theneutral position,

Whenthe control bar 38 is lowered at its right hand end in Figure 1 therotor 2| assumes the p osi-tion shown Figure 4. The circuit may n ow Ifsuch load exceeds the predetermined safe load for the particular hoist yin question, as soon as the .load is almost sulllciently supported licythe hook 3| the link 23 .will open enough to per'- mit ,the switch blade2 2 to .move away iroin the contact connected with the terminal Ii inthe limtswitch thus breaking the cirouitto the ning coil RC.y thecircuit usually having been broken to the starting coil SQ 4hy the motorcorningun to sneedaud due to thecentriiugal .switch Cshavingonenedlf.the load is. imposed the hoist before the starting coil .hashoerige-energized by opening of the centrifugal switch. the opening oithe limit switch will breals the oircuit to the starting coil alsoi hoththestarting coil .and the running coil in the un circuit oftheinotorwhich includes thelimitswitcn vlilith the limit .switch oneri the rnotorcan he reversed yhowever,as the-,limit switch is not the downcircuitwhich may he traced in Figure 5 from-li through l0, l, I 1, 2, .CSpSGA2i! and l to 9, part oiithe current dividing at Zand passing throughi3., 6., upwardly through RC, sand -I 9- 'lhus the starting coilislenergized in the saine direction as in the up circuit, .but therunning .coil isenergiged in the reverse direction for-revers: ing the.motor ,and the current from. the supply terminal does not have to gothrough the limit switch Whlh Would be open vas illustrated in Figure 5due to having operated in its safety capacity by reason oi aload.,imposed on the hoist After the load is released, all or part of it maybe removed and the hoist again operated in the normal manner. Thearrangement is such however that when the hoist is rendered inoperativeby an overload it can still be operated in the lowering direction forreleasing the load. In order to prevent the U-shaped link 23 from beingopened excessively, I provide a screw 39 threaded into the arm andadaptable to engage a shoulder 40 of the lower arm of the U-shanedmeinher 23 after the arrn has been spread sufficiently toopen theV limit switch T-1S. The operating point of the limiting switch may beadjusted by means of the screw 25 and the screw 39 is then adjusted to apoint where it permits opening of the limit switch and a slightaddiltional amount oi' opening movement of the U.

Some changes ,may be made in the construction and arrangement of theparts of my device withoutdeparting from the real spirit and purpose o fmy invention, and it is my intention to `'cover by my claims anymodified forms of structure 2or use of mechanical equivalents which maybe reasonably included within their scope.

25 l claim as my invention.:

l. ty load limiting ineens .for hoists and the l c comprising amechanical connecting link of erna ihle character, a switch carried.thereby ve to the weight oi the load on. ,said being physicallyinterposed the ist and connected in the un circuit of th hoisting motorindependent of the down oircuit thereoft 2. Safety load limiting meansof the character switch yheine normally ,closed and havingan actuatingelerneiit responding to spreading of `said loon underload, to be openedwhen the load is greater than a. predetermined value.

3: Eoruse a hoist motor or the like having a switch providedwithindenendent un and-down circuits: a load. responsivelinhmechanically con.- nected between the hoist and a support therefor,a safety load limiting switch Supported by said linkv and normallyclosed unon normal loads andonened hy imposing excessive loads on thehoisty said switch heine: electrically connected in the.,

hoist. being operative to open a circuit therethrough and beingelectrically connected in .the

ative.

5. A safety load limiting -switchv electrically in terposed in theVlifting circuit only of a hoist, ,and means for operating said switchcomprising a Cs. shaped element which isrextensible in proportion to theload imposed thereon, normally cooperates with said'limiting switchtoretain the same closed4 and permits the same toopen upon the load e x.ceeding a predetermined value.

5 c. n saiety ieee limiting switch nir the. uam

disclosed ,comprising loon shaped frame onen` .te same unen an attemptbeing made to hoist greater than a predetermined load, said.

up circuit of .the hoist motor to render it inlopencircuit only of ahoist, and means for operating said switch comprising a loop elementopen at one side and extensible in proportion to the load imposedthereon, normally cooperates with said limiting switch to retain thesame inoperative, and permits the same to operate to render `the liftingcircuit inoperative upon the load exceeding a predetermined Value. Y

RALPH R. DILLON.

REFERENCES CITED The following references are of record in the file ofthis patent:

6 UNI'I'ED STATES PATENTS Number Name Date Darlington Aug. 21, 1906Johnson Feb. 24, 1925 Hallenbeck Dec. 13, 1932 Nelles Apr. 24, 1945Manney et al Oct. 9, 1945 Roy Nov. 12, 1946

